Ulf Harnhammar found two stack overflows and two directory traversal
vulnerabilities in LHa version 1.14 and 1.17. A stack overflow occurs when
testing or extracting archives containing long file or directory names.
Furthermore, LHa doesn't contain sufficient protection against relative or
absolute archive paths.

Impact

The stack overflows can be exploited to execute arbitrary code with the
rights of the user testing or extracting the archive. The directory
traversal vulnerabilities can be used to overwrite files in the filesystem
with the rights of the user extracting the archive, potentially leading to
denial of service or privilege escalation. Since LHa is often interfaced to
other software like an email virus scanner, this attack can be used
remotely.

Workaround

There is no known workaround at this time. All users are advised to upgrade
to the latest available version of LHa.